Many industrial printing systems are able to print on both sides of a web or roll of media. Some duplex web printing systems, such as high-speed printing systems, may use one print engine for printing on one side of a web, and a second print engine for printing on the reverse side of a web.
When printing on both sides of a web it is important that pages printed on each side of the web are not only correctly aligned opposite one another, but also that the correct printed page is printed on each side of the web. This ensures that when the web is cut into individual sheets the pages on each side of each sheet correspond. For example, when printing double-sided personalized correspondence, such as bank statements, medical records, salary statements, etc., it is critical that the recto and the verso pages of each sheet of media correspond to the same individual.